Digital imaging systems, such as those employed for converting still color photographic film (e.g. 35 mm) images into digital format for storage in a digital database and subsequent playback, as by way of a color television monitor, customarily encode the output of an opto-electronic film scanning device to some prescribed resolution and store the encoded image in an associated database as a respective image file. When it is desired to display a particular stored image, the contents of the respective addresses of the database in which the digitized image has been stored are read out and coupled to display driver circuitry for energizing corresponding pixels on the TV monitor.
Because each frame of a typical roll of 35 mm film has different horizontal and vertical frame dimensions, for example a dimension of 36 mm in the horizontal direction, parallel to the lengthwise direction of the film, and a dimension of 24 mm in the vertical direction, orthogonal to the lengthwise direction of the film (a horizontal:vertical aspect ratio of 3:2), a photographer often rotates the camera ninety degrees about the lens axis in order to capture a subject in what is conventionally referred to as a `vertical` condition. Since the digitizing mechanism that scans the film strip digitizes each frame as though it contains a `horizontally shot` image, then, when a `vertically shot` image is displayed, it will be rotated unless the recording and playback system has been designed to accommodate vertical images.
One conventional approach to handle the problem, similar to that described in the U.S. Pat. No. to Ohta, No. 4,641,198, is to rotate those film frames which contain vertical images by ninety degrees before scanning and to fill in the left and right sides of the image with a uniform `border` color (e.g. black). Although this scanning method will provide the proper orientation of the displayed image, it suffers from two drawbacks. First, the actual scanning mechanism must be modified to effect a rotated scan of the vertical images. This is conventionally accomplished by physically reorienting the film by ninety degrees and changing the lens magnification of the scanning device by an amount related to the frame aspect ratio. Secondly, since side borders, which contain no useful information in terms of the captured image, are also recorded, some of the information storage capacity of the recording medium is wasted. A second solution to the problem is to rotate the display device, which is obviously impractical in many applications.
A third solution is to allow for different image orientations to be stored, together with digital control data indicative of the orientations of the images, and to employ an image playback device designed to read the orientation control data to properly orient the images on playback. Some conventional computer image file formats, for example, the Tag Image File Format (TIFF), Revision 5.0, developed jointly by Aldus Corporation, Seattle, Washington, and Microsoft Corporation, Redmond, Washington, and described in "An Aldus/Microsoft Technical Memorandum, Aug. 8, 1988, include the provision for an optional "tag", which can be used to indicate the orientation of the image. Page 25 of this document describes the TIFF `orientation tag`, which can have eight different values, indicating whether the zeroth row and zeroth column of the pixel data matrix represents the top and left, top and right, bottom and right, bottom and left, left and top, right and top, right and bottom, or left and bottom of the visual image, respectively. However, the Aldus document further states that such a field is recommended for private (non-interchange) use only. The default condition, where the zeroth row represents the visual top of the image, and the zeroth column of the pixel data matrix represents the visual left hand side of the image, is recommended for all non-private applications, including those involving importing and printing. Thus, the TIFF orientation tag is never used to re-orient for display images which have been stored in different orientations in an image database.
In addition to the problem of different image orientations, captured images may have different aspect ratios. For example, dedicated use panoramic cameras, such as the Kodak Stretch (.TM.) camera have an aspect ratio of 3:1 which is considerably wider than the above-referenced 3:2 aspect ratio of conventional 35 mm cameras. Other camera types, such as those which employ 126 type film also have aspect ratios other than 3:2.